byzantium: Move wys packaging to separate repo

We want to base on Debian packaging like phosh, calls, ...

byzantium.yml

@@ -51,4 +51,5 @@ webkit:
   deb_build_options: ['nocheck', 'parallel=4']
   deb_build_profiles: ['nocheck']
 wlroots: {}
-wys: {}
+wys:
+  url: https://source.puri.sm/Librem5/debs/pkg-wys.git